This invention relates generally to a nonwoven fabric or web which is formed from meltblown fibers of thermoplastic polyethylene resin, as well as the process of producing such a fabric.
Thermoplastic resins have been extruded to form fibers and webs for a number of years. The most common thermoplastics for this application are polyolefins, particularly polypropylene. Other materials such as polyesters, polyetheresters, polyamides and polyurethanes are also used for this purpose. Each material has its characteristic advantages and disadvantages visa vis the properties desired in the final product to be made from such fibers.
Nonwoven fabrics are useful for a wide variety of applications such as diapers, feminine hygiene products, incontinence products, towels, medical garments and many others. The nonwoven fabrics used in these applications are often in the form of laminates like spunbond/meltblown/spunbond (SMS) laminates. In SMS laminates the exterior layers are generally spunbond polypropylene which are usually present for strength, and the interior layer which is generally meltblown polypropylene and is usually present as a barrier layer.
It is desirable that the meltblown barrier fabric layer have good barrier properties yet also be as soft and drapeable as possible. Polypropylene meltblown fabrics, while usually possessing good barrier properties, are not as soft and drapeable as polyethylene fabrics. Polyethylene meltblown fabrics are generally very soft and drapeable yet usually lack the requisite barrier properties. The lack of sufficient barrier properties in polyethylene meltblown fabrics is thought to be due to the inability to form uniformly fine fibers or due to the tendency to generate "shot", an imperfection which causes gaps or holes in the webs.
It is an object of this invention to provide a meltblown fabric which has barrier properties comparable to polypropylene meltblown fabric yet with the softness and drapeability common to polyethylene fabrics.